Table of Isotopic Masses and Natural Abundances This table lists the mass and percent natural abundance for the stable nuclides. The mass of the longest lived isotope is given for elements without a stable nuclide. Nuclides marked with an asterisk (*) in the abundance column indicate that it is not present in nature or that a meaningful natural abundance cannot be given. The isotopic mass data is from G. Audi, A. H. Wapstra Nucl. Phys A. 1993, 565, 1-65 and G. Audi, A. H. Wapstra Nucl. Phys A. 1995, 595, 409-480. The percent natural abundance data is from the 1997 report of the IUPAC Subcommittee for Isotopic Abundance Measurements by K.J.R. Rosman, P.D.P. Taylor Pure Appl. Chem. 1999, 71, 1593-1607. Z
1
Name
Symbol
Mass of Atom (u)
% Abundance
Hydrogen
1
1.007825
99.9885
Deuterium
2
2.014102
0.115
Tritium
3
3.016049
*
H H H
Symbol
Helium
3
3.016029
0.000137
4
4.002603
99.999863
He He
15
Phosphorus
31
30.973762
16
Sulphur
32
31.972071
94.93
33
32.971458
0.76
34
33.967867
4.29
36
S
35.967081
0.02
35
Cl
34.968853
75.78
37
36.965903
24.22
36
35.967546
38
37.962732
0.0632
40
39.962383
99.6003
39
38.963707
93.2581
40
39.963999
0.0117
41
K
40.961826
6.7302
40
Ca
39.962591
96.941
42
41.958618
0.647
P
S S
17 3
Lithium
6
6.015122
7.59
7
7.016004
92.41
Li Li
4
Beryllium
Be
9.012182
Chlorine
Cl
18 9
Argon
100
Ar Ar Ar
5
Boron
10
10.012937
19.9
11
11.009305
80.1
B B
19
Potassium
K K
6
Carbon
12
12.000000
98.93
13
13.003355
1.07
14
14.003242
*
C C C
20
Calcium
Ca
7
Nitrogen
99.632
43
42.958767
0.135
15
15.000109
0.368
44
43.955481
2.086
46
45.953693
0.004
48
47.952534
0.187
45
44.955910
16
15.994915
99.757
17
16.999132
0.038
18
17.999160
0.205
O O O
9
Fluorine
Ca Ca
19
F
18.998403
100
Ca
21
Scandium
22
Titanium
Sc
Neon
45.952629
47
46.951764
7.44
Ti
19.992440
90.48
48
47.947947
73.72
21
20.993847
0.27
49
48.947871
5.41
9.25
50
49.944792
5.18
Ne
22
21.991386
23
22.989770
Ne
12
Sodium
Magnesium
8.25
20
Ne
11
100
46
Ti
10
0.3365
14.003074
N
Ca
Oxygen
100
14
N
8
% Abundance
Name
S
2
Mass of Atom (u)
Z
Na
100
24
23.985042
78.99
25
24.985837
10.00
26
25.982593
11.01
Mg Mg Mg
Ti Ti Ti
23
24
Vanadium
Chromium
50
49.947163
0.250
51
V
50.943964
99.750
50
Cr
49.946050
4.345
52
51.940512
83.789
53
52.940654
9.501
54
Cr
53.938885
2.365
Mn
54.938050
V
Cr Cr
13
Aluminum
27
14
Silicon
28
27.976927
92.2297
29
28.976495
4.6832
30
29.973770
3.0872
Al
Si Si Si
26.981538
100
25
Manganese
55
26
Iron
54
53.939615
5.845
56
55.934942
91.754
Fe Fe
100
Z
Name
Mass of Atom (u)
% Abundance
57
56.935399
2.119
58
57.933280
0.282
Symbol Fe Fe
Z
Name
38
Strontium
Mass of Atom (u)
% Abundance
84
83.913425
0.56
86
85.909262
9.86
87
86.908879
7.00
88
87.905614
82.58
Symbol
Sr Sr
27
Cobalt
59
Co
58.933200
100
Sr Sr
28
Nickel
58
57.935348
68.0769
60
59.930791
26.2231
61
60.931060
1.1399
62
61.928349
3.6345
64
63.927970
0.9256
Ni Ni Ni Ni Ni
39
Yttrium
89
Y
88.905848
40
Zirconium
90
Zr
89.904704
51.45
91
90.905645
11.22
92
91.905040
17.15
Zr Zr
29
Copper
63
62.929601
69.17
94
93.906316
17.38
65
64.927794
30.83
96
Zr
95.908276
2.80
64
63.929147
48.63
66
65.926037
27.90
67
66.927131
4.10
68
67.924848
70
69.925325
Cu Cu
30
Zinc
Zn Zn Zn Zn Zn
Zr
41
Niobium
93
Nb
92.906378
42
Molybdenum
92
Mo
91.906810
18.75
94
93.905088
9.25
0.62
95
94.905841
15.92
96
95.904679
16.68
96.906021
9.55
97.905408
24.13
Mo
99.907477
9.63
Mo Mo Mo
31
Gallium
69
68.925581
60.108
97
71
70.924705
39.892
98
Ga Ga
Mo Mo
100
32
Germanium
70
69.924250
20.84
72
71.922076
27.54
73
72.923459
7.73
74
73.921178
36.28
Ge Ge Ge Ge
76
Ge
75.921403
Arsenic
75
As
74.921596
Selenium
98
Tc
97.907216
*
44
Ruthenium
96
Ru
95.907598
5.54
98
97.905287
1.87
99
98.905939
12.76
100
99.904220
12.60
101
100.905582
17.06
7.61
Ru
100
Ru
74
73.922477
0.89
102
101.904350
31.55
76
75.919214
9.37
104
103.905430
18.62
77
76.919915
7.63
78
77.917310
23.77
102.905504
80
79.916522
49.61
82
81.916700
8.73
Se Se Se Se Se Se
Ru Ru
45
Rhodium
103
46
Palladium
102
101.905608
1.02
104
103.904035
11.14
Rh
Pd Pd
35
Bromine
78.918338
50.69
105
104.905084
22.33
81
80.916291
49.31
106
105.903483
27.33
108
107.903894
26.46
110
109.905152
11.72
107
106.905093
51.839
109
Ag
108.904756
48.161
106
Cd
105.906458
1.25
108
107.904183
0.89
Br
Pd Pd Pd
Krypton
78
77.920386
0.35
80
79.916378
2.28
82
81.913485
11.58
Kr Kr Kr
83
82.914136
11.49
84
83.911507
57.00
86
85.910610
17.30
Kr Kr Kr
Pd
47
48
Silver
Cadmium
Ag
Cd
37
Rubidium
100
79
Br
36
14.84
Technetium
Ru
34
100
43
Ru
33
100
85
84.911789
72.17
110
109.903006
12.49
87
86.909183
27.83
111
110.904182
12.80
Rb Rb
Cd Cd
Z
Name
Symbol
Mass of Atom (u)
% Abundance
24.13
137
136.905821
11.232
12.22
138
137.905241
71.698
138
137.907107
0.090
139
La
138.906348
99.910
136
Ce
135.907144
0.185
138
137.905986
0.251
111.902757 112.904401
114
113.903358
28.73
116
115.904755
7.49
Cd Cd Cd
Indium
% Abundance
113
Cd
49
Mass of Atom (u)
112
113
112.904061
4.29
115
114.903878
95.71
In In
Z
Name
Symbol Ba Ba
57
58
Lanthanum
Cerium
La
Ce
50
Tin
112
111.904821
0.97
140
139.905434
88.450
114
113.902782
0.66
142
141.909240
11.114
115
114.903346
0.34
116
115.901744
14.54
117
116.902954
7.68
118
117.901606
24.22
119
118.903309
120
Sn Sn Sn Sn
Ce Ce
140.907648
142
Nd
141.907719
27.2
8.59
143
142.909810
12.2
119.902197
32.58
144
143.910083
23.8
122
121.903440
4.63
145
144.912569
8.3
124
123.905275
5.79
146
145.913112
17.2
148
147.916889
5.7
121
120.903818
57.21
150
Nd
149.920887
5.6
123
122.904216
42.79 Pm
*
Sn Sn Sn Sn Sn
Praseodymium
60
Neodymium
141
Pr
Sn
59
Nd Nd Nd Nd Nd
51
Antimony
Sb Sb
52
53
54
55
56
Tellurium
Iodine
Xenon
100
61
Promethium
145
144.912744
62
Samarium
144
143.911995
3.07
0.89
147
146.914893
14.99
123.902819
4.74
148
147.914818
11.24
124.904425
7.07
149
148.917180
13.82
120
Te
119.904020
0.09
122
Te
121.903047
2.55
123
Te
122.904273
124
Te
125
Te
Sm Sm Sm Sm
126
Te
125.903306
18.84
150
149.917271
7.38
128
Te
127.904461
31.74
152
151.919728
26.75
130
Te
129.906223
34.08
154
153.922205
22.75
151
150.919846
47.81
153
Eu
152.921226
52.19
152
Gd
151.919788
0.20
127
I
126.904468
100
124
Xe
123.905896
0.09
126
Xe
125.904269
0.09
Sm Sm Sm
63
64
Europium
Gadolinium
Eu
128
Xe
127.903530
1.92
154
153.920862
2.18
129
Xe
128.904779
26.44
155
154.922619
14.80
130
Xe
129.903508
4.08
156
155.922120
20.47
131
Xe
130.905082
21.18
157
156.923957
15.65
132
Xe
131.904154
26.89
158
157.924101
24.84
134
Xe
133.905395
10.44
160
159.927051
21.86
136
Xe
135.907220
8.87
Cs
132.905447
Gd Gd Gd Gd Gd Gd
65
Terbium
159
66
Dysprosium
Tb
158.925343
156
Dy
155.924278
0.06
0.106
158
157.924405
0.10
131.905056
0.101
160
159.925194
2.34
134
133.904503
2.417
161
160.926930
18.91
135
134.905683
6.592
162
161.926795
25.51
136
135.904570
7.854
163
162.928728
24.90
Cesium
133
Barium
130
129.906310
132
Ba Ba Ba Ba Ba
100
100
Dy Dy Dy Dy Dy
Z
Name
Symbol 164
Dy
67
Holmium
68
Erbium
165
Ho
Mass of Atom (u) 163.929171
164.930319
% Abundance 28.18
100
189.959930
0.782
194
193.962664
32.967
167
166.932045
22.93
195
194.964774
33.832
168
167.932368
26.78
196
195.964935
25.242
170
Er
169.935460
14.93
198
Pt
197.967876
7.163
Tm
168.934211
167.933894
0.13
169.934759
171
78
Platinum
Pt Pt Pt Pt
0.014
79
Gold
197
Au
196.966552
80
Mercury
196
Hg
195.965815
3.04
198
197.966752
9.97
170.936322
14.28
199
198.968262
16.87
172
171.936378
21.83
200
199.968309
23.10
173
172.938207
16.13
201
200.970285
13.18
174
173.938858
31.83
202
201.970626
29.86
176
175.942568
12.76
204
203.973476
6.87
175
174.940768
97.41
176
175.942682
2.59
174
173.940040
0.16
176
175.941402
177
176.943220
Yb Yb Yb Yb Yb Yb Yb
Lu Lu
Hf Hf Hf
100
29.524 70.476
204
Pb
203.973029
1.4
5.26
206
205.974449
24.1
18.60
207
206.975881
22.1
208
207.976636
52.4
180
179.946549
35.08
180
Ta
179.947466
0.012
181
Ta
180.947996
99.988
180
179.946706
0.12
182
181.948206
26.50
183
182.950224
14.31
184
183.950933
30.64
186
185.954362
28.43
W W
Hg
204.974412
13.62
W
Hg
202.972329
27.28
W
Hg
Tl
178.945815
W
Hg
Tl
177.943698
Hf
Hg
81
82
Thallium
Lead
Pb Pb Pb
83
Bismuth
209
Bi
208.980383
100
84
Polonium
209
Po
208.982416
*
85
Astatine
210
At
209.987131
*
86
Radon
Rn
222.017570
*
87
Francium
Fr
223.019731
*
88
Radium
226
Ra
226.025403
*
227.027747
*
Th
232.038050
100
Pa
231.035879
100
222
223
185
184.952956
37.40
187
186.955751
62.60
89
Actinium
227
184
183.952491
0.02
90
Thorium
232
186
185.953838
1.59
187
186.955748
1.96
91
Protactinium
231
188
187.955836
13.24
189
188.958145
16.15
92
Uranium
190
189.958445
192
191.961479
Re Re
Os Os Os Os Os Os Os
0.15
205
179
Hf
Hg
100
203
178
Hf
Osmium
Pt
33.61
170
76
190
165.930290
168
Rhenium
62.7
166
Ytterbium
75
192.962924
191.961035
70
Tungsten
37.3
Ir
Ir
192
169
74
190.960591
193
1.61
Thulium
Tantalum
191
163.929197
69
73
% Abundance
0.14
Er
Hafnium
Iridium
Mass of Atom (u)
161.928775
Er
Er
72
77
Symbol
164
Er
Lutetium
Name
162
Er
71
Z
Ac
234
234.040946
26.26
235
235.043923
0.7200
40.78
238
238.050783
99.2745
U U U
0.0055
Z
Name
Symbol
93
Neptunium
237
94
Plutonium
244
95
Americium
96
Curium
97
Berkelium
98
99
Np
Mass of Atom (u)
% Abundance
237.048167
*
Pu
244.064198
*
243
Am
243.061373
*
247
247.070347
*
247
247.070299
*
Californium
251
251.079580
*
Einsteinium
252
Es
252.082972
*
Fm
257.095099
*
Md
258.098425
*
No
259.101024
*
Cm
Bk
Cf
100
Fermium
257
101
Mendelevium
258
102
Nobelium
259
103
Lawrencium
262
Lr
262.109692
*
104
Rutherfordium
263
Rf
263.118313
*
105
Dubnium
262
Db
262.011437
*
106
Seaborgium
266
266.012238
*
107
Bohrium
264
Bh
264.012496
*
108
Hassium
269
Hs
269.001341
*
109
Meitnerium
268
Mt
268.001388
*
110
Ununnilium
272
Uun
272.001463
*
111
Unununium
272
272.001535
*
112
Ununbium
277
(277)
*
114
Ununquadium
289
(289)
*
116
Ununhexium
289
(289)
*
118
Ununoctium
293
(293)
*
Sg
Uuu
Uub
Uuq
Uuh
Uuo